Field
The present disclosure generally relates to battery-operated systems, and, more particularly, to voltage regulators for battery operated systems.
Description of the Related Art
Mobile telephones and other portable systems are typically powered by a rechargeable battery, such as a lithium-ion (Li-ion) battery. These batteries are popular because they have high energy density suitable for extended operation of the portable device. When the batteries need to be charged, the portable device can be connected to a charger that plugs into a power source such as an outlet or a vehicle's power system. However, to charge the battery, the voltage from the charger (e.g., 5.5 or more volts) can be significantly greater than the normal operating voltage of the battery (e.g., 2.3-4.5 volts). Since a user of the portable device may want to be able to use the device when it is being charged, the circuitry in the device needs to be able to handle the higher than normal voltages present during charging.
Unfortunately, much of the circuitry in the portable device is made using integrated circuit technologies that may not be able to be directly powered via the battery. As transistor feature sizes decrease, the components (e.g., MOSFETs) on the integrated circuit can break down at voltages well below the maximum voltage that the battery will experience. One solution to this problem is to use voltage regulators that step-down the battery voltage to a voltage that the integrated circuits can safely tolerate.